Filter cartridges for filtering fluids, such as engine oil, are known in the art. Oil filter cartridges are used in internal combustion engines to remove contaminants from the lubricating oil. This reduces engine wear and promotes longer engine life.
The typical oil filter cartridge has a canister or housing with a filter element contained therein which filters oil as it flows through the housing. The housing typically has one end adapted for attachment to the engine block by use of an internally threaded centrally located fluid exit port that threads onto a corresponding externally threaded configuration on the engine block. Oil flows into the housing through fluid inlet holes surrounding the exit port, and filtered oil is returned to the engine through the fluid exit port. The cartridge is typically sealed to the engine block by use of an O-ring gasket around the inlet holes. Fluid filters with such an arrangement for attachment are referred to in the art as "spin-on" filter cartridges.
Disposable or "throw-away" type fluid filters are known in the art. The filter element is permanently sealed within the housing. When the filter element has become clogged with contaminants, the entire cartridge is discarded and a new unit is put in its place. This type of filter is unnecessarily wasteful in that a whole new unit must be used each time the filter cartridge is serviced. As only the filter element has been expended, the useful life of the other individual components has not been utilized. This results in a substantial loss as to the cost of materials and labor that go into manufacturing these components.
Much attention has been recently given to the adverse environmental effects of throw-away filters. Many millions are disposed of each year. Some are thrown in the trash and end up in landfills, often with a substantial amount of oil still contained therein. State and local governments have passed legislation to reduce the adverse environmental impact of disposable filters. Some regulations requires a 24-hour period of drainage to remove excess oil. Others require crushing to reduce volume. In fact, regulations in many areas treat used oil filters as "hazardous waste" requiring special care in their disposal. Substantial fees are often charged for the service of disposal of used filters, such fees often being as high as one-half the purchase price of the filter.
An oil filter cartridge having a detachable cover to permit replacement of the filter element itself is known in the art. U.S. Pat. No. 5,066,391 discloses such a filter cartridge. However, such prior art designs are relatively expensive in that a heavy gauge outer wall for the housing and a separate bottom end cap are required.
The present invention is concerned with a solution to these problems. What has been needed is a simple, low-cost, easy to manufacture, spin-on fluid filter cartridge with a replaceable filter element.